Helicopter rotors are usually so designed that the pitch of the rotor blade can be varied to produce different thrust levels. Recent rotor hub designs, and in particular rotor hub designs employing a flexible strap interconnecting the rotor blades, have introduced a new design constraint into the design of rotor pitch change mechanisms. Conventional rotor pitch change mechanisms, if used with a strapped rotor, produce an undesirable vertical movement of the rotor blade, because the root end of the rotor blade is not constrained against vertical motion. This vertical motion of the blade (heaving) results in long excursions of the associated pitch control mechanism, since much of the travel of the linkage is required simply to follow the blade movement.